Liner hanger

ABSTRACT

A liner hanger for down-hole suspension of a liner pipe from a well casing. Toothed slips are used to engage the casing wall when allowed to slide up over a conical slip expander. Bow springs attached to the slips frictionally engage the casing wall, and cause the slips to move up onto the slip expander when a latch mechanism is released. An hydraulically operated latch release device is disclosed, employing a sleeve biased away from the latches but forced toward the latches by hydraulic pressure. Control is provided by increasing the pressure in the tubing string compared to the annulus between the casing and the tubing. The latching arrangement may be both hydraulically and manually operated, according to one embodiment.

United States Patent [72] Inventors Truman Foy Wilson;

Fletcher Andrew Anderson; Ben Rodney Groce, Odessa, Tex. [21] AppLNo. 832,046 [22] Filed .lunell, 1969 [45] Patented Mar.l6,l971 [73] Assignee Brown Well Service & Supply Company Odessa,Tex.

[54] LINERHANGER 20 Claims, 6 Drawing Figs.

[52] U.S.Cl 166/208, 26612.1 [51] lnt.Cl. ..E2 1b 23/00, E2lb43/10 [50] FieldofSearch 166/138, 208,216,217

[56] References Cited UNITED STATES PATENTS 942,739 12/1909 Palm 166/138 2,633,918 4/1953 LeRouax..... 166/138x 2,716,457 8/1955 LeRouax 166/138x l3 ml 76 77-;

Primary Examiner-Ian A. Calvert Attorney-Arnold, White & Durkee ABSTRACT: A liner hanger for down-hole suspension of a liner pipe from a well casing, Toothed slips are used to engage the casing wall when allowed to slide up over a conical slip expander. Bow springs attached to the slips frictionally engage the casing wall, and cause the slips to move up onto the slip expander when a latch mechanism is released. An hydraulically operated latch release device is disclosed, employing a sleeve biased away from the latches but forced toward the latches by hydraulic pressure. Control is provided by increasing the pressure in the tubing string compared to the annulus between the casing and the tubing. The latching arrangement may be both hydraulically and manually operated, according to one embodiment.

Patented arch 1, 1971 FIG.4

H. 7 Mmw 7. E Wilson,

FAAnderson 8 B.R.Groce IN VE N TORS BY W,

A TTORNEYS LINER HANGER A liner hanger is a tool employed in oil wells when the well is being completed, and functions to suspend a liner pipe within a well casing which has been previously set within the well bore. In one typical well completion sequence, a liner pipe is attached to the bottom of the liner hanger, the liner pipe is run into the oil production zone, and the liner hanger is actuated to grip the casing wall. Then the tubing string used to run the liner and liner hanger down into the well is released and withdrawn. The hanger may be thus required to support long lengths of liner pipe, sometimes weighing many tons. .Yet, the liner hanger must occupy only a very narrow radial distance because a casing diameter is selected for maximum economy consistent with the production capability of the well, while the liner will be selected as the maximum which will fit within the casing. The liner hanger preferably has the same ID (inside diameter) as the liner pipe to permit tools for other completion operations to pass through.

Liner hangers have been provided which are actuated by mechanisms such as a so-called J-hook or other mechanical means which require certain rotary or reciprocating motions of the string to cause the hanger to be actuated to grip the easing wall. These devices are widely used, but yet have been found to inadvertently actuate the hanger due to motion of the string while running in, or to be inoperative after run-in. Further, many of these mechanically operated devices are found to cause difficulty in releasing the hanger, when it is desired to remove the liner for resetting into another protection zone or if it is erroneously set.

Hydraulically set liner hangers have been provided which operate by circulating the well, i.e'., applying fluid pressure to the tubing string and withdrawing liquid from the annulus between the string and the casing. Usually pressure is permitted to build up only after a ball is dropped down the string to seat in a catcher. This type of hanger avoids the problem of prematurely setting the hanger when running in, since impact, rotation or vertical movement will not cause it to set. However, these hydraulically set hangers do not provide the same degree of positive operation such as results from the use of bow springs to move the slips, as in the mechanically set devices. Further, release of the hanger after it has been set is not facilitated in the hydraulically set devices currently available.

It is therefore an important feature of this invention to provide a liner hanger which is set by hydraulically operated latching means that cannot be inadvertently actuated by rotation, reciprocation or impact, while at the same time employing positive mechanical means, such as bow springs which frictionally engage the casing walls, for the purpose of providing the axial mechanical movement of the slips when the hanger is being set. Another feature of the invention is the provision of a liner hanger wherein the actuating and setting mechanism requires a very narrow radial thickness. Another feature is the provision of a liner hanger which may be set and also released in a positive manner, but yet is relatively free of inadvertent setting while running in or the like.

In accordance with this invention, a liner hanger is provided which includes slips which are caused to move onto a slip expander by bow springs, but the slips and bow springs are latched by mechanical detents which may be released by a hydraulically operated mechanism. This latch release arrangement includes a sleeve movable axially along the tubular body of the liner hanger, with latch spring expanders positioned at one end of the sleeve to force the latches out away from the detents. The sleeve is caused to move by a pressure differential applied between the interior and exterior of the tubing string. In this manner, mechanical operation of the bow springs and slips is provided, but the latch release mechanism is hydraulically operated.

Novel features which are believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as further features and advantages thereof, may best be understood by reference to the following detailed description of illustrative embodiments, when read in conjunction with the accompanying drawing, wherein:

FIG. 1 is a vertical sectional view of a portion of a well bore having a casing therein, and including a liner hanger according to the invention shown in elevation, with parts thereof broken away or in section;

FIG. 2 is an enlarged detail view in vertical section, of a portion of the liner hanger of FIG. 1, showing in particular the hydraulically operated latching mechanism;

- FIG. 3 is an enlarged detail view in section similar to that of FIG. 2, but showing another embodiment of the invention;

FIG. 4 is a pictorial view of a catch ring which may be used in the liner hangers of FIGS. 1-3, according to one embodiment of the invention; and

FIGS. 5a and 5b are enlarged detail views, in vertical section, of the operation of the latching mechanism using the catch ring of FIG. 4.

Referring now to FIG. 1, a liner hanger according to the invention is shown within a well casing 10 which has been set in a well bore. The liner hanger is shown in an unactuated condition, although it is in a position where it would be actuated and set, since a depending liner 11 is shown in a producing formation 12. The liner hanger, and the liner pipe 11 attached below it, are lowered into the casing by a tubing string or drill pipe i3 which is connected to the upper end of the liner hanger mechanism by a releasable connector or setting tool 14 which may be any one of a number of conventional devices. The setting tool will not be described in detail here as the releasable mechanism forms no part of this invention. After the liner hanger has been actuated and set in the well casing 10 to suspend the liner pipell in the proper location in the well bore, the tubing string 13 is appropriately operated to actuate the releasable connector 14 so that the tubing string may be withdrawn from the well, leaving the liner and liner hanger in place for production.

The liner hanger includes a conically shaped slip expander FIG. which is secured to the outside of a tubular body 16 that generally supports all of the parts of the liner hanger. Located below the slip expander 15, and functioning to ride up on the slip expander and be forced out against the walls of the FIG. casing 10, are a number of slips 17 which include teeth for gripping the wall of the casing. Although three slips 17 are shown, spaced at 120 it is also conventional and perhaps preferable to use four or six such slips suitably spaced around the tubular body 16. Each of the slips is secured to an extension 18 of a separate bow spring or spring stabilizer 19. All three of the bow springs 19 are secured by rivets to a collar 20 which slides freely along the tubular body 16 and merely functions to stabilize the slips with respect to peripheral movement. The bow springs are shaped to normally assume a position larger than the inside diameter of the well casing 10, so that when lowered down into the casing the bow springs will frictionally engage the casing wall. Thus when the latch release mechanism is actuated as will be described, and the string with attached liner hanger is further lowered, the frictional engagement of the bow springs on the casing wall will I cause the slips 17 to move up into engagement with the slip expander 15, causing the slips to move radially outward and grip the casing.

The lower ends of the bow springs 19 are all connected by rivets to another collar 21 which moves freely along the tubular body 16 and functions to guide the bow springs and keep them in place. Connection to this collar also anchors the latch springs and prevents inward deflection of the bow springs from unlatching the hooks as discussed below. Extending below the bow springs and integrally connected thereto, are elongated latch springs 22. Each of these includes a hook or *detent 23 formed on the lower end and adapted to engage a catch ring 24. A safety ring 25 similar to the catch ring 24 is positioned above the catch ring to prevent the slips from moving too far in the event that the slips do not engage the casing wall properly. The catch ring 24 and the safety ring 25 are both circular bands secured to the tubular body l6 by welding or the like.

The latch springs 22 and hooks 23 are caused to disengage from the catch ring 24 by a hydraulically operated mechanism including a cylindrical sleeve 26 which is slidably disposed outside the tubular body 116. At the upper end of the cylindrical sleeve is conical or wedge-shaped latch expander 27 which, when the sleeve 26 is forced upward, moves under the hooks 23 and forces them outward so that the books will clear the catch ring 24. Upward movement of the sleeve 26 is caused by a hydraulic piston and cylinder-type arrangement as will be described. initially, during lowering of the liner hanger and liner into the well, upward movement of the sleeve 26 is prevented by a set of three shear pins 28 which are disposed beneath the latch hooks 23. These shear pins extend into holes suitably provided in the tubular body l6, and are composed of a material which is fairly rigid, but falls under the force produced by the hydraulic actuating mechanism.

The hydraulic sleeve 26 is caused to move upward by admission of liquid under pressure from the interior of the tubular body 16 into a hydraulic chamber 29 through one of a plurality of hydraulic injection holes 30 spaced around the tubular body. The sleeve 26 is ordinarily held down against a stop ring 31 by a flat helical spring 32 which surrounds the tubular body 16. The spring 32 may be seen in FIG. 1 through open ports 33 which allow the pressure in the annular space between the tu bular body 16 and the hydraulic sleeve 26 to be equalized with the pressure between the outer periphery of the liner hanger and the well casing 10, except of course within the chamber 29. Below the stop ring 31, the tubular body 16 extends down to a suitable coupling mechanism 34 which in turn is connected to the liner 11. Included within this section may be a valve arrangement which permits the pressure within the tubing string 13 and the tubular body 16 of the liner hanger to be greater than the pressure within the annulus between the tubing string and the well casing 10, in spite of the apertures in the liner 11 or other outlets, but still permits subsequent production of oil. Various setting tools are available which have elongated extensions with packers or cups provided for this purpose.

Referring now in particular to FIG. 2, which is an enlarged detail view of the latch arrangement and hydraulic setting mechanism referred to with reference to FIG. 1, it will be noted that the chamber 29 is defined between an enlarged collar 36 at the upper end of and integral with the sleeve 26, and a cylindrical collar 37 secured to the body 16 by welding or the like. The chamber 29 is sealed at top and bottom by rings 38 positioned in suitable recesses in the collar 36 and 0- rings 39 positioned in suitable recesses in the collar 37. The helical spring 32 bears against the lower side of the collar 37, while the lower end of the spring 32 bears against another collar 40 so that force is applied by the spring against the collar 40 to hold the collar 40 against the stop ring 31. However, when pressure inside the tubular body 16 increases, the liquid will push against the lower transverse face of the collar 36 within the chamber 29, forcing the sleeve 26 upward and fracturing the shear pins 28. This will permit the conicallatch spring expander 27 to engage the mating surface of the hooks 23 and force the hooks outward so that they will pass over the catch ring 24. It is noted that a shoulder 41 is provided at the top of the sleeve 26 to engage the ends of the latch springs and books 22 and 23, functioning to force the latch springs upward in case the conical expander 27 does not completely disengage the hooks and thus the hooks do not freely pass over the catch ring 24. The shoulder All also functions to prevent the latch springs from passing down over the sleeve 26, when the hanger is disengaged and is being retrieved.

After the latch hooks FIG. have been disengaged from the catch ring 24 as just described, the string is lowered further and the frictional engagement of the bow springs on the casing wall causes the bow springs and slips to move upward and thus the slips will grip the casing wall. Later, if it is necessary to remove the liner, the liner hanger is released by pulling up on the string so the slip expander is pulled away from FIG. slips. The bow springs will then cause the latch spring to move downward and the hooks 23 will again engage the catch ring.

If the slips do not readily break free of the wall, the weight of tubing string may be used to free the slips by lowering the tubing string slightly.

Referring now to FIG. 3, an embodiment of the invention is shown wherein the helical spring 32 which is used in the embodiment of FIGS. 1 and 2, is replaced by a hydraulic arrangement for reversing the direction of movement of the hydraulic sleeve 2a. In the FIG. 3 embodiment, all of the parts are the same as discussed above, with the hydraulic sleeve 26 surrounding the tubular housing 16 and providing a chamber 29 which is sealed by O-n'ngs 38 and 39 so that a pressure differential forcing fluid into the hole 30 will cause the hydraulic sleeve 26 to move upward. In addition however, the sleeve 26 includes exterior ports 44 which admit fluid from the annulus 45 between the well casing it) and the sleeve, whereby a pressure differential between the annulus and the interior of the tubing string and tubular body 16 will cause the hydraulic sleeve 26 to move downward until the collar 40 engages the stop ring 311 in a manner the same as the function provided by the spring 32 in the previous embodiment. It is noted that a set of O-rings 36 are provided in suitable recesses in the collar 40 in the FIG. 3 embodiment to provide sealing in the usual hydraulic piston and cylinder arrangement. Although not shown in FIG. 3, the remainder of the liner hanger would be the same as in FIGS. 1 and 2, including the slip expander, slips, bow springs, and latching arrangement, or a latching arrangement as seen in FIGS. 4 and 5 may be used.

In reference to FIG. 4, another embodiment of the invention is shown wherein a different form of catch ring 24 is used so that both manual and hydraulic operation is provided. In the embodiment of FIGS. 1 and 2, the catch ring 24 is a solid ring so that regardless of where the hooks 23 are positioned around the ring, the hooks will still engage the ring, and rotation of the tubing string has no effect on the operation of the hanger. However, the catch ring 24 of FIG. 4 is especially shaped to provide a climb out slot" 48 for each of the spring hooks 23. That is, if three bow springs and latch springs are used, there would be three of the slots 48 provided in the catch ring 24, spaced at 120. In like manner, if four or six latch springs were used, four or six climb-out slots 48 would be employed. As long as the latch spring hook 23 is generally vertically aligned with the open part of the slot 48, the hook will engage the ring 24'. However, if the tubing string and liner hanger mechanism is rotated clockwise looking down, a cam surface 42 engages the hook 23 and causes it to move up onto the smooth cylindrical outer face of the catch ring to a position 50 where it will then slide on over the catch ring and allow the slips of the liner hanger to move up and grip as before. The operation of the embodiment using the catch ring of FIG. 4, is seen from FIGS. 5a and 5b where the latch hook is shown in the engaged and in the disengaged positions, respectively. The

- embodiments of the liner hanger of FIGS. 1 and 2, or FIG. 3,

may be adapted for manual as well as hydraulic operation by using the catch ring of FIGS. 4 and 5.

Accordingly, although the invention has been described with reference to particular embodiments, it is seen that modifications of the disclosed embodiments, as well as other embodiments of the invention, will occur to persons skilled in the art upon reference to this disclosure.

We claim:

1. A liner hanger of the type used in a well casing, comprismg:

a generally tubular body for supporting the parts of the liner hanger;

a plurality of slips slidably mounted on the exterior of the body for gripping a well casing;

conically shaped, downwardly facing, slip expanding means mounted on said body for causing the slips to move radially into gripping engagement with the well casing, as the slips are displaced axially upward into engagement with the expanding mean;

a plurality of bow springs for resiliently and frictionaily engaging the well casing, connected to the slips and axially movable with the slips;

elongated latch spring means including a plurality of elongated flat springs depending from and coupled to the slips and bow springs, and radially movable between hold and release positions, the slips being held away from engagement with the slip expanding means when the latch spring means is in the hold position, the slips being permitted to move axially into engagement with the slip expanding means when the latch spring means is in the release position, each of the latch spring means including a hook positioned to engage a catch ring when in the hold position and to disengage the catch ring upon outward radial movement;

hydraulically operated axially movable means positioned for mechanical engagement with the latch spring means and effective to radially displace the latch spring means from the hold to the release position, the lower end of each of the latch spring means including a slanted surface engageable by a mating slanted surface on the hydraulically operated means; and

the hydraulically operated means including a hydraulic piston provided at one end of an elongated sleeve, means including the sleeve defining a chamber, and means are provided for admitting fluid into the chamber to operate the piston when the pressure within the liner hanger exceeds the pressure in the annulus between the liner hanger and the well casing.

2. A liner hanger according to claim l wherein the hydraulically operated means includes an elongated sleeve defining a hydraulic piston and defining a chamber whereby a hydraulic piston and cylinder function is provided.

3. A liner hanger according to claim 2 wherein the latch spring means extend axially above the elongated sleeve, and include hook means each having a lower end operatively engageable by the upper end of the elongated sleeve.

4. A liner hanger according to claim 3 wherein detents are provided on said body and the hook means are spring-biased inward and are releasable from said detents upon outward radial movement.

5. A liner hanger according to claim 1 wherein the catch ring includes a plurality of slots for engaging the hooks of the latch spring means, and also a plurality of hook expanding surfaces adjacent the slots adapted to move the hooks to the release position upon rotation of the slips with respect to the liner hanger.

. 6. A liner hanger according to claim 1 wherein the sleeve is biased in a direction away from engagement of the hydraulically operated means with the latch spring means.

7. A liner hanger according to claim 6 wherein biasing of the sleeve is provided by a flat helical spring within the sleeve.

8. A liner hanger according to claim 6 wherein biasing of the sleeve is provided by means including a second hydraulic piston provided at the other end of the sleeve, and means for admitting fluid into a chamber to operate the piston when the pressure within the line hanger is less than the external pressure in the annulus between the liner hanger and the well casmg.

9. A liner hanger according to claim 6 wherein the slips, bow springs, latch spring means and the elongated sleeve are all slidably mounted on a tubular body for the liner'hanger, and the slip expanding means and the catch ring are fixedly mounted on the tubular body.

It). A liner hanger comprising:

a plurality of slips for gripping a well casing;

conically shaped, downwardly facing, slip expanding means for causing the slips to move radially into gripping engagement with the casing wall, as the slips are displaced axially upward into engagement with the expanding means;

a plurality of bow springs for resiliently and frictionally engaging the casing wall, connected to the slips and axially movable with the slips;

elongated latch spring means coupled to the slips and bow springs, and radially movable between hold and release positions, the slips being held away from engagement with the slip expanding means when the latch spring means is in the hold position, the slips being permitted to move axially into engagement with the slip expanding means when the latch spring means is in the release position; and

hydraulically operated, axially movable means positioned for mechanical engagement with the latch spring means from the hold to the release position, the hydraulically operated means being held from engaging the latch spring means by frangible shear pin means, the hydraulically operated means including an elongated sleeve having a shaped upper end for engaging the latch spring means, and said frangible shear pin means being positioned between said shaped upper end of the sleeve and the latch spring means.

1 l. A liner hanger comprising:

a generally tubular body for supporting the parts of the liner hanger;

a plurality of toothed slips positioned on the tubular body in sliding relationship for gripping the interior cylindrical wall of a well easing or the like;

wedgelike slip expanding means positioned on the tubular body in fixed relationship for causing the slips to move radially against the wall as the slips are displaced axially upward into engagement with the expanding means;

a plurality of bow springs slidably positioned on the tubular body for frictionally engaging the casing wall, the bow springs being connected to the slips and axially movable with such slips;

latch means coupled to the slips and bow springs, and movable between hold and release positions, the slips being held away from engagement with the slip expanding means when the latch means is in the hold position and being permitted to move axially into engagement with the slip expanding means when the latch means is in the release position; and

hydraulically operated means, including an elongated sleeve surrounding the tubular body, slidably positioned on the tubular body and axially movable between hold and release positions, and effective when in the release position for engagement with the latch means to displace the latch means from the hold to the release position, the latch means being positioned above the elongated sleeve and including hook means having a lower end operatively engageable by the upper end of the elongated sleeve.

12. A liner hanger according to claim 11 wherein the hook means are spring biased inward and are releasable from detent means fixed to the tubular body, upon outward radial movement of the hooks caused by engagement of the upper end of the elongated sleeve.

' 13. A liner hanger according to claim 12 wherein the hook means includes downwardly facing slanted surfaces, and wherein the upper end of the elongated sleeve includes a mating slanted surface.

14. A liner hanger according to claim ll wherein the latch means include a plurality of elongated flat springs depending from the bow springs, and the lower end of each such latch spring includes a slanted surface engageable by a mating slanted surface on the hydraulically operated means.

15. A liner hanger according to claim 1 wherein each of the latch springs includes a hook positioned to engage a catch ring which is fixed to the tubular body.

16. A liner hanger according to claim 15 wherein a second ring is positioned on the tubular body above the catch ring for engagement by the books after a given distance of axial movement by the bow springs and slips.

1'7. A liner hanger according to claim 11 wherein the hydraulically operated means includes a hydraulic piston provided at one end of an elongated sleeve, means including the sleeve defining a chamber behind the piston, and means for admitting fluid into the chamber to operate the piston when the pressure within the liner hanger is different from the pressure in the annulus between the liner hanger and the well casmg.

piston provided at the other end of the sleeve, and means for admitting fluid into a chamber to operate the second piston when the pressure withinthe liner hanger is different from the external pressure in the annulus between the liner hanger and the well casing, and the differential is opposite that for operating the first-mentioned hydraulic piston. 

1. A liner hanger of the type used in a well casing, comprising: a generally tubular body for supporting the parts of the liner hanger; a plurality of slips slidably mounted on the exterior of the body for gripping a well casing; conically shaped, downwardly facing, slip expanding means mounted on said body for causing the slips to move radially into gripping engagement with the well casing, as the slips are displaced axially upward into engagement with the expanding mean; a plurality of bow springs for resiliently and frictionally engaging the well casing, connected to the slips and axially movable with the slips; elongated latch spring means including a plurality of elongated flat springs depending from and coupled to the slips and bow springs, and radially movable between hold and release positions, the slips being held away from engagement with the slip expanding means when the latch spring means is in the hold position, the slips being permitted to move axially into engagement with the slip expanding means when the latch spring means is in the release position, each of the latch spring means including a hook positioned to engage a catch ring when in the hold position and to disengage the catch ring upon outward radial movement; hydraulically operated axially movable means positioned for mechanical engagement with the latch spring means and effective to radially displace the latch spring means from the hold to the release position, the lower end of each of the latch spring means including a slanted surface engageable by a mating slanted surface on the hydraulically operated means; and the hydraulically operated means including a hydraulic piston provided at one end of an elongated sleeve, means including the sleeve defining a chamber, and means are provided for admitting fluid into the chamber to operate the piston when the pressure within the liner hanger exceeds the pressure in the annulus between the liner hanger and the well casing.
 2. A liner hanger according to claim 1 wherein the hydraulically operated means includes an elongated sleeve defining a hydraulic piston and defining a chamber whereby a hydraulic piston and cylinder function is provided.
 3. A liner hanger according to claim 2 wherein the latch spring means extend axially above the elongated sleeve, and include hook means each having a lower end operatively engageable by the upper end of the elongated sleeve.
 4. A liner hanger according to claim 3 wherein detents are provided on said body and the hook means are spring-biased inward and are releasable from said detents upon outward radial movement.
 5. A liner hanger according to claim 1 wherein the catch ring includes a plurality of slots for engaging the hooks of the latch spring means, and also a plurality of hook expanding surfaces adjacent the slots adapted to move the hooks to the release position upon rotation of the slips with respect to the liner hanger.
 6. A liner hanger according to claim 1 wherein the sleeve is biased in a direction away from engagement of the hydraulically operated means with the latch spring means.
 7. A liner hanger according to claim 6 wherein biasing of the sleeve is provided by a flat helical spring within the sleeve.
 8. A liner hanger according to claim 6 wherein biasing of the sleeve is provided by means including a second hydraulic piston provided at the other end of the sleeve, and means for admitting fluid into a chamber to operate the piston when the pressure within the line hanger is less than the external pressure in the annulus between the liner hanger and the well casing.
 9. A liner hanger according to claim 6 wherein the slips, bow springs, latch spring means and the elongated sleeve are all slidably mounted on a tubular body for the liner hanger, and the slip expanding means and the catch ring are fixedly mounted on the tubular body.
 10. A liner hanger comprising: a plurality of slips for gripping a well casing; conically shaped, downwardly facing, slip expanding means for causing the slips to move radially into gripping engagement with the casing wall, as the slips are displaced axially upward into engagement with the expanding means; a plurality of bow springs for resiliently and frictionally engaging the casing wall, connected to the slips and axially movable with the slips; elongated latch spring means coupled to the slips and bow springs, and radially movable between hold and release positions, the slips being held away from engagement with the slip expanding means when the latch spring means is in the hold position, the slips being permitted to move axially into engagement with the slip expanding means when the latch spring means is in the release position; and hydraulically operated, axially movable means positioned for mechanical engagement with the latch spring means from the hold to the release position, the hydraulically operated means being held from engaging the latch spring means by frangible shear pin means, the hydraulically operated means including an elongated sleeve having a shaped upper end for engaging the latch spring means, and said frangible shear pin means being positioned between said shaped upper end of the sleeve and the latch spring means.
 11. A liner hanger comprising: a generally tubular body for supporting the parts of the liner hanger; a plurality of toothed slips positioned on the tubular body in sliding relationship for gripping the interior cylindrical wall of a well casing or the like; wedgelike slip expanding means positioned on the tubular body in fixed relationship for causing the slips to move radially against the wall as the slips are displaced axially upward into engagement with the expanding means; a plurality of bow springs slidably positioned on the tubular body for frictionally engaging the casing wall, the bow springs being connected to the slips and axially movable With such slips; latch means coupled to the slips and bow springs, and movable between hold and release positions, the slips being held away from engagement with the slip expanding means when the latch means is in the hold position and being permitted to move axially into engagement with the slip expanding means when the latch means is in the release position; and hydraulically operated means, including an elongated sleeve surrounding the tubular body, slidably positioned on the tubular body and axially movable between hold and release positions, and effective when in the release position for engagement with the latch means to displace the latch means from the hold to the release position, the latch means being positioned above the elongated sleeve and including hook means having a lower end operatively engageable by the upper end of the elongated sleeve.
 12. A liner hanger according to claim 11 wherein the hook means are spring biased inward and are releasable from detent means fixed to the tubular body, upon outward radial movement of the hooks caused by engagement of the upper end of the elongated sleeve.
 13. A liner hanger according to claim 12 wherein the hook means includes downwardly facing slanted surfaces, and wherein the upper end of the elongated sleeve includes a mating slanted surface.
 14. A liner hanger according to claim 11 wherein the latch means include a plurality of elongated flat springs depending from the bow springs, and the lower end of each such latch spring includes a slanted surface engageable by a mating slanted surface on the hydraulically operated means.
 15. A liner hanger according to claim 14 wherein each of the latch springs includes a hook positioned to engage a catch ring which is fixed to the tubular body.
 16. A liner hanger according to claim 15 wherein a second ring is positioned on the tubular body above the catch ring for engagement by the hooks after a given distance of axial movement by the bow springs and slips.
 17. A liner hanger according to claim 11 wherein the hydraulically operated means includes a hydraulic piston provided at one end of an elongated sleeve, means including the sleeve defining a chamber behind the piston, and means for admitting fluid into the chamber to operate the piston when the pressure within the liner hanger is different from the pressure in the annulus between the liner hanger and the well casing.
 18. A liner hanger according to claim 17 wherein the sleeve is biased in a direction away from engagement of the hydraulically operated means with the latch means.
 19. A liner hanger according to claim 18 wherein biasing of the sleeve is provided by flat helical spring means within the sleeve.
 20. A liner hanger according to claim 18 wherein biasing of the sleeve is provided by means including a second hydraulic piston provided at the other end of the sleeve, and means for admitting fluid into a chamber to operate the second piston when the pressure within the liner hanger is different from the external pressure in the annulus between the liner hanger and the well casing, and the differential is opposite that for operating the first-mentioned hydraulic piston. 